1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same. Particularly, the present invention relates to a semiconductor device having a multi-layered wiring structure including air-gaps, and a method of manufacturing the same.
Priority is claimed on Japanese Patent Application No. 2008-276484, filed Oct. 28, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
Recently, semiconductor devices having a multi-layered wiring structure have been manufactured. Such a semiconductor device includes wires vertically and horizontally provided in each layer, contact plugs electrically and vertically connecting the wires in different layers, and an inter-layer low-permittivity film covering gaps among wiring portions for reducing capacities among the wires.
However, wires are densely provided, and wire intervals are small in recent years, causing an increase in a parasitic capacity affecting one wire and preventing high speed operation.
Various methods of reducing capacities among wires have been proposed. For example, Japanese Unexamined Patent Application, First Publication No. 2003-163264 discloses a copper interconnect of an air gap formed by: alternately forming wiring portions and inter-layer insulating films with the desired layout; and wet-etching the inter-layer insulating film made of a silicon oxide film to form gaps among the wiring portions. Instead of the inter-layer insulating film, gaps are provided among the wiring portions in this structure, thereby enabling a reduction in capacities among the wires. This structure is called an air-gap structure, an air isolation structure, or an air-gap isolation structure.
However, the wiring portions are supported only by contact plugs. For this reason, long wires that are longer than 1 mm, such as power supply wires, are used for upper wiring portions. The long wires sag under their own weight. Consequently, the sagged long wires contact other wires in a lower layer, thereby causing the upper and lower wires to short out, or the long wires to fracture.
Japanese Unexamined Patent Application, First Publication No. 2004-327909 discloses a semiconductor device having an air-gap structure including a support plug to prevent fracture of wires. However, the support plug is made of an insulating material different from the material forming the wires, thereby causing a complicated manufacturing process.